Question

Explain what is capillarity and where can one see it except in chromatography.

Answer 1

Capillarity or capillary action is the ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity. The effect can be seen in the drawing up of liquids between the hair of a paint-brush, in a thin tube, in porous materials such as paper and plaster, in some non-porous materials such as sand and liquefied carbon fibre etc. It occurs because of the difference in intermolecular forces between the liquid molecules and surrounding solid surfaces (i.e., difference between cohesion and adhesion). If the diameter of the tube is sufficiently small, then the combination of surface tension (which is caused by cohesion within the liquid) and adhesive forces between the liquid and container wall act to lift the liquid up against the gravity.